How serious do I take "last frost date"?

Here in Indianapolis our last frost date is April 18th, but the weather here has been fantastic and I feel like I should start transplanting seeds into my SFG beds. How serious should I take the "last frost date"? What kind of indicators should I use to determine when to start transplanting?

Here in central PA the rule of thumb is to plant after Memorial day. I try to watch the extended weather forcasts. It seems every year we get a few cold nights before Memorial day. It only takes one frost to ruin your plants. If you don't have alot of plants you can cover them. I usually have over 40 tomato and pepper plants, so I wait. I may put a couple of tomatos out early. If I lose them it's not a big deal.

Scott

I only have two 4'x4' beds now so it wouldn't be that big of a deal to cover, but it just seems safer to leave everything in the cold frame for a couple more weeks just to be sure.

What do I look for in my local weather forecast to know there is a frost on a particular night? Is it just looking for when the low for the night gets to like 32 degrees or will they actually say "frost"?

I listened to our local weather forecast this morning for Southeast Missouri, and even though we've had daytime temps in the 80's, the weatherman warned us they are calling for scattered light frost next week when the temp is forecast to dip to 37 degrees on Tuesday night. It all depends on the cloud cover, the dew point, etc. Usually our local weatherman figures it all out for us and warns us when to worry about our plants. If you have a local agricultural forecast, that would be the one to tune in to.

There is a difference between a frost and a freeze warning. Some plants will survive a frost but not a freeze. Some will get burned back by a frost but will come out of it and still live, while some plants are so tender that even a light frost will kill them. Most fruit trees will survive a hard freeze, but if they are in blossom, those buds which are in full bloom will be killed, but those that haven't yet bloomed will often be okay. I've seen strawberry blossoms turn black in the center after a freeze. Those did not produce fruit, but the blooms that came later did just fine.

For me, I've found that planting tender plants too early doesn't gain me much in growing time as they just seem to sit there until the weather warms up. Plants I set out a few weeks later may produce fruit only a few days later than the early transplants.

Hardy plants are not affected by frost, and some aren't bothered by freezes. I've seen potato foliage freeze down to the ground twice, and still come back to produce a bumper crop.

frost dates are being updated by many official sources. The traditional frost dates are 100 year dates. My thought is this -

IF you are transplanting something that is easily replaceable, or

IF you can protect your boxes in the event of a frost, or

IF you are transplanting things that can handle frost, then go for it.

I have peas, both transplants and seeds, beets, radishes, scallions, swiss chard, arugula, baby pak choi and carrots. I think all these guys will be fine, but I have more seeds ready to go if they get nailed. By the way, I also have broccoli that I would transplant out but I am worried about the heat - I have been told many times that they are more dependable in the fall for this very reason.

and then you have years like two years ago when a killing frost hit the southeast about two weeks after the last frost date.... it wiped out my grapevines for that year.

You can't control the weather.... I planted some stuff yesterday that I usually would have planted after May 1st... I just have a feeling "in my bones" that we won't have a killing frost this year.

My mentality this year is monitor the temp at about 5PM each day and be ready to cover up my boxes if its going to get cold during the night. I've already bought my rolls of plastic to do this...

One good thing about a SFG.... its a whole lot easier to cover one of them up then a traditional garden!

Our last frost date is normally around June 1st, but having an SFQ since last spring, I think I can get around that with heavy row cover or plastic covers, and even towels if need be.
We broke a record at 85 yesterday but that's not normal. You can't go by unusually early warm days. The weather will change to normal in less than a week, as it did here. We're going to have low 30s nites and even to a flat 30 and high 40s and low 50s days for the next couple of weeks
I adjusted my garden plan this year to a last frost date of May 15th. It only takes a few minutes to go outside and cover the rows or crops when we have so few raised beds. Its another experiment to try. If it works, I might change it to May 1st next year.